In regard to natural air-modifying agents that repel vermin, there are a number of aromatic oils, such as peppermint, eucalyptus and spearmint which are well known and sold commercially for this purpose. An example is the Mouse Away line of products from Dreaming Earth Botanicals. Peppermint oil can be a key ingredient in a rodent repelling solution. The delivery method for the Mouse Away products is simply to use an absorbing medium which is impregnated with their proprietary blend of spearmint and peppermint oils. The device is placed in the desired location and the vapor evaporates from all of the exposed surfaces of the device. Additionally, simply soak a cotton ball and place it in the desired location. This simple device will function in the same manner, repelling rodents for a relatively short period of time. One disadvantage of this “Soaked Cotton Ball” approach is the non-constant delivery rate of the peppermint oil vapor from such a device. The Mouse Away products are essentially equivalent to the “soaked cotton ball” in that an absorbing material is saturated with the oil solution and simply allowed to evaporate from there.
In this basic soaked cotton ball approach, the evaporative surface will be soaked to its highest level at the start and as the material evaporates, the surface concentration will drop. The vapor delivery rate, which is proportional to surface area and concentration at that surface, will then be a maximum at the start of the operation of the device and will simply decrease with time. Since it is generally desirable to modify the air for the desired purpose both at a particular level and for the longest period of time possible, it is readily apparent that this approach accomplishes neither. Because the delivery rate decreases with time, it must be designed to be significantly higher than required at the start in order to gain an appreciable lifetime of operation. In other words, excess vapor delivery is required at the start of operation.
For the case of repelling rodents, it can be appreciated that a certain concentration of vapor is required to effectively repel them from an area. At some point the simple soaked cotton ball device dries out to the extent that the concentration of the evaporating vapor falls below an effective level and the device ceases to function as desired. In such a simple device, the only time that the device produces the minimum but effective dose is just prior to the device becoming ineffective.
Clearly, one main disadvantage of this simple soaked cotton ball approach is that the delivery rate of the vapor is not optimized. The vapor delivery rate must necessarily be at or above the required level to start, and then will continually decrease, falling below the desired level at some point in time. The maximum total lifetime of the device is attained by soaking the absorbing material until it is completely saturated. This non-uniform delivery is the primary cause of the short lifetime of these devices as the initial saturated device typically delivers vapor in excess of that required.
Another disadvantage of these simple devices is that to extend the lifetime requires a manual procedure to refill the device or replace it, and there is no provision for being able to retrieve such a device conveniently from a remotely deployed location. In addition, although these devices can be tossed into some remote locations, they are not specifically designed for this type of deployment and therefore may not operate effectively.
There are also delivery methods for providing an air modifying agent that are energized devices, i.e. they rely on stored energy, such as a battery, or require electrical power. Requiring electrical power from a household outlet necessarily limits the ability to locate the device in hard to reach locations. Likewise, a battery operated device suffers from the disadvantages of either (1) the size or mass required for conventional sized batteries, or (2) the expense and short lifetime of typical button-sized batteries. Additionally, the difficulty of changing a battery is complicated in the application of the device in difficult to reach locations.
The most familiar example of a vapor delivery device is a common air-freshener, where an aromatic substance, in liquid form, is contained in a vented container. The method of delivery of an air-modifying agent includes an integrated liquid reservoir connected to an evaporative surface. The liquid is then internally transported to an evaporative surface from which the air-modifying vapor emanates. These devices generally contain a reservoir of the desired vapor in liquid form, an evaporative surface from which the liquid solution evaporates and a delivery mechanism which transports the liquid continually from the reservoir to the evaporative surface. These types of reservoir containing evaporative sources are well known as air-modifying devices and are commonly used as “air fresheners” or “insect repelling devices”. During operation, the liquid air modifying ingredient is continually transported to the evaporative surface, typically through wicking or capillary action, without the application of external power. From the evaporative surface, the desired liquid solution evaporates into the surrounding air flow through apertures or vents. The air modifying ingredient then evaporates into the surrounding air until the reservoir is depleted.
This integrated reservoir method is typically able to achieve a more constant delivery rate of the desired vapor and thus increase the lifetime of the device. The primary disadvantage of the integrated-reservoir air freshener, as described in the prior art, can be appreciated once one considers remotely deploying such a device by tossing or rolling. The existing devices were never intended, nor designed, to be tossed, rolled or thrown. Particularly, these devices do not contain any combination of design features required to accomplish remote deployment.